More than 18,000 police and military have been put on high alert ahead of an upcoming rally to protest Jakarta’s non-Muslim governor for alleged blasphemy. Messages from Islamists and foreign jihadists are said to be behind the calls for violence.

A threat from thousands of Islamists, both foreign and domestic, has prompted President Joko Widodo to instruct Indonesia’s military to be at the ready ahead of the second largest demonstration this month against Governor Basuki Tjahaja Purnama.

Regularly criticized for being a Christian governor in a majority-Muslim city, Purnama, who is also known as Ahok, recently called out his opponents for interpreting a verse in the Koran to mean that Muslims shouldn’t cooperate with Christians and Jews. Ahok stated that his rivals were “lying,” which resulted in Islamic hardliners exploding in protest, and the president telling the military on Monday to be “on alert.”

The verse in question is number 51 from the fifth sura of the holy book, which some argue should be understood exactly as written, while others point out that it was written at a time of war, and caution against literal interpretations.

Although Indonesia officially subscribes to a moderate form of Islam, it is also the world’s largest Muslim-majority nation, and is known to suffer from bursts of sporadic violence against Buddhist and Christian minorities.

There are many Islamic lobby groups and organizations in the country, but the upcoming rally is largely the work of the Islamic Defenders Front (FPI) – a militant organization known for staging violent demonstrations. The same group unsuccessfully tried to block Ahok from becoming governor on religious grounds in 2014.

The problem isn’t so much FPI, whose membership is quite small, but another group called the Nandlatul Ulama, which has 40 million Indonesian members and also believes Ahok should be tried for blasphemy, although it has called on Muslims to boycott Friday’s rally.

Moreover, the country’s top clerical body, the Ulama Council, also supports the view that Ahok must stand trial, and that a non-Muslim can’t lead Muslims.

Consequently, support for the anti-Ahok demonstration capitalizes on both religious sentiment and political differences. Senior figures supporting Ahok’s opponent in the upcoming February gubernatorial election are also thought to be involved. Their candidate, Anies Baswedan, is currently running behind Ahok.

Fears of a possible outbreak of violence at Friday’s upcoming rally stem from information circulating online and offline suggesting that thousands of Muslims from across the country may take to the streets of Jakarta to protest.

It is thought that the problem is being exacerbated by foreign jihadists. A threatening photo allegedly sent by Syria-based Al-Nusra Front, an Al Qaeda-linked group that now calls itself the Jabhat Fatah al-Sham, emerged last month that seems to bear this out, as it shows several armed militants holding a message reading “Punish Ahok or our bullets will,” as translated by the Sydney Morning Herald.

The paper spoke to Nasir Abas, an Indonesian police consultant who was once a terrorist himself, according whom there is a danger that both Islamic State (IS, formerly ISIS/ISIL) and Al Qaeda supporters will converge on Jakarta this Friday.

“In Syria, those two groups are rivals,” Abas said. “But in Indonesia they can be united because there is a common enemy. In their view, it is Ahok.”

Militants have also sent out an instructional message through the Telegram app, which attempts to incite Indonesian Muslims to emulate an IS supporter who recently wounded three police officers near Jakarta, according to terrorist expert Sydney Jones

“The instruction says something like: ‘Follow the example of the brave young man in Tangerang. Take advantage of the thousands of police deployed during the protest’,” Jones told SMH. “They are being urged to follow the example and stab people.”

According to Jones’ own editorial posted on the website of Lowey Institute, “Indonesia’s spineless political leaders have allowed extremists to seize the momentum and foment religious hatred against the governor – who happens to be an ethnic Chinese Christian – for more than a month without challenging the substance or methods of their arguments. Now this hatred is culminating in a march on Jakarta on Friday 4 November that even has jihadists in Syria actively urging violence.”

Meanwhile, Police Chief General Tito said in a statement, “I appeal to everyone to stay calm. Do not be easily provoked by social media.” Although Tito noted that 18,000 police and 500 military personnel will be present on November 4, he maintained there were no specific instructions to use live ammunition if the demonstration got out of control.

Indonesian Military (TNI) spokesman Brig-Gen Wuryanto, who confirmed the plans, said that “the military has encouraged Islamic organizations not to send members to Jakarta… We hope they will listen to our advice,” according to Malaysia’s The Star Online,

Ahok himself remains undeterred and has vowed to continue campaigning. Judging from the current polls, the governor looks set to win reelection in February. He is a close ally to president Widodo, who also served as Jakarta’s governor for 18 months before becoming president and handing the reigns over to Ahok.